Interoperability between the communication systems of local, state and federal agencies became of paramount importance as a result of the terrorist attacks to the United States on Sep. 11, 2001. In response to these events, the U.S. Department of Homeland Security (DHS) was created to facilitate a national effort to prevent and respond to such acts of terrorism. A major component of the DHS' domestic preparedness initiatives is the ability of First Responders to an emergency situation (including those from local, state and federal agencies) to communicate during the crisis.
One difficulty in accomplishing interoperability between the communication systems of local, state and federal agencies results from the differences in these systems, which include, but are not limited to, differences in radio types, modes and operating frequencies. One way of addressing this difficulty in interoperability is to design a solution based upon any known similarities between the systems. One obvious similarity is that essentially all of the communication systems for local, state and federal agencies provide for a plain media interface (e.g., base-band analog audio, base-band analog video, plain data, etc.) and typically have access to packet-switched communication systems (or networks). A packet-switched network is defined herein as a network that serves as the medium through which messages may be transmitted between two endpoints or nodes (e.g., between a source and a destination), wherein the message is broken down into a set of units commonly referred to as “packets,” and the packets are transferred across the network.
A commonly used packet-switched network is an Internet Protocol (IP) based network, wherein the message is packetized and routed over the network using the Internet Protocol. The Internet Protocol is an open standard network layer (Layer 3 of the Open Standard Interconnection (OSI) model) routing protocol defined in the Internet Engineering Task Force (IETF) Request for Comment (RFC) 791 and any subsequent corresponding RFC updates as recognized in the art. Since IP-based networks are the types of networks most prevalently used by local, state and federal agencies, existing interoperability solutions are, accordingly, IP-based. Such IP-based solutions are desirable mainly because they do not require a costly and, quite frankly, unrealistic replacement of equipment that would be necessary to conform the existing communication systems of all of the various agencies to the same type of radio system, equipment and standards.
Moreover, existing solutions are based upon a client-server networking approach, wherein a client system that wants to be interconnected with another client system must first communicate with a third-party application (i.e., a server) to facilitate the interoperability and resultant communication with the other client system. However, such client-server based solutions suffer from major shortcomings. For example, these solutions generate a single point of failure at the interoperability server site, such that if the server is not functioning properly, interoperability is severely inhibited if not rendered impossible. In addition, expansion of systems using these client-server based solutions may become costly. Generally, a single server in accordance with the interoperability solution will have a maximum capacity, and when that capacity is reached, additional servers will be required. This may significantly increase the cost of the solution, thereby possibly making it cost prohibitive for some government agencies, especially the smaller ones that typically have fewer resources that may be dedicated to such solutions.
Thus, there exists a need for a method and apparatus for interoperability between packet-switched systems such as, for instance, IP-based systems that does not require a client-server based approach but that also enables interoperability using a peer-to-peer networking structure. It is further desirable that the solution be capable of expansion with minimal cost.